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The construction process of splicing and installing the chimney cylinder and supporting steel structure according to the design and technical standards. A chimney is a special structure that discharges the flue gas, steam and all harmful gases generated by industrial furnaces, equipment and devices in factories and workshops into the atmosphere. The height of the chimney mainly depends on the nature of the exhaust flue gas, the emission volume and the diffusion conditions of the atmosphere, and is determined by calculation according to the national atmospheric health standards. Its structural types include brick masonry structure, reinforced concrete structure and steel structure. Steel chimneys are often used in metallurgical plants, and the most common one is a single cylindrical steel chimney. The height of a steel chimney is generally tens of meters. The self-supporting steel chimney of a large heating furnace in a metal processing workshop can be as high as 80m.
There are four installation methods for steel chimneys: upright installation, inverted installation, overall lifting and mechanical lifting and inverted installation.
Upright installation method: Using selected lifting equipment, such as crawler or truck cranes, the pre-assembled chimney lifting units are hoisted and fixed in place from bottom to top in the order of the bottom, body and cap. It is usually used for the installation of general small and medium-sized single or multiple combined steel chimneys. When the lifting equipment conditions permit, large steel chimneys can also be installed in the upright installation method.
Inverted installation method: Three mast cranes are set up at equal distances around the chimney installation location, and the chimney belts are installed in reverse order from top to bottom. The specific steps are: first assemble the barrel cap belt at the installation position, lift it with a mast crane, assemble the next belt under the barrel cap, and weld and fix the belt to the barrel cap; then lift it with a mast crane, put in the next belt, continue to assemble, weld, fix, and then lift it again, and repeat this cycle until a section of the barrel bottom is put in; fix the barrel bottom to the foundation, and then connect and fix it with the barrel body, and the chimney installation is completed. The inverted installation method can reduce high-altitude operations and facilitate assembly and welding. When there is no large self-propelled crane, using 2 to 3 masts as cranes and installing chimneys by inverted installation is still a desirable construction method. The inverted installation method is suitable for the installation of small and medium-sized single chimneys. In order to ensure the overall stability, when the chimney is lifted, 3 to 6 cables must be set around the barrel cap to help the simplified body not tilt due to excessive height when lifting. Tightening the cables during assembly can temporarily fix the barrel body.
Overall lifting method: Small and medium-sized single chimneys are often constructed by overall lifting method. Before lifting, an assembly stand is set up on the ground, and the chimney is assembled into a whole on the stand. The chimney is lifted, positioned and fixed as a whole using a gantry or herringbone mast crane, or a large crawler crane or truck crane.
Hydraulic jacking and inverted installation method: For ultra-high large steel chimneys with a tower frame structure and a height of more than 100m, when large cranes (such as 3000kN cranes) are not competent for the lifting of the entire chimney, the hydraulic jacking and inverted installation method can be used. The main steps of the hydraulic jacking and inverted installation method are: jacking construction, tower frame installation, chimney welding and installation measurement.
The main steps of jacking construction are as follows:
(1) Set up 4 to 6 small hydraulic jacks of the same model with a total jacking force of about 1.5 times the weight of the entire chimney at the chimney installation location, and connect them in parallel with the high-pressure oil pump station with pipelines so that they can operate synchronously and work alone to support and adjust the height of the installed cylinder section and the verticality of the cylinder.
(2) A working platform is set up on the small hydraulic jack, and the installation position of the chimney is marked on the platform. The chimney top cylinder and the cap are installed by a crane in the upright installation method. The height of the cylinder is determined by the overall construction plan of the chimney.
(3) Three lifting pillars are set up on the outer periphery of the installed chimney, which are calculated to fully meet the lifting needs. A large hydraulic jack and its auxiliary equipment with a lifting force of about 0.5 times the total weight of the chimney are set up on each pillar, and they are connected in parallel with the high-pressure oil pump with pipelines so that they can operate synchronously and work alone.
(4) A movable inner ring beam is set about 500mm inside the lower mouth of the chimney section, and a movable outer ring beam is set outside. When the inner ring beam expands outward and the outer ring beam contracts inward, the cylinder can be clamped. Three lifting holes are also set on the outer ring beam and aligned with the three lifting pillars.
(5) When the lifting begins, start the high-pressure oil pump to lift the small hydraulic jack under the cylinder synchronously, so as to adjust the height of the cylinder section, and align the lifting hole on the outer ring beam with the pin hole on the lifting tie rod, insert the No. 1 pin and fix it. At this time, insert the No. 2 pin on the upper part of the three large hydraulic jacks on the lifting support into the tie rod hole and fix it. Start the three large hydraulic jacks synchronously to drive the chimney cylinder held tightly by the lifting tie rod and the outer ring beam to rise. When the three large hydraulic jacks have lifted one stroke, insert the No. 3 positioning pin into the tie rod hole so that the weight of the chimney is transmitted to the lifting support through the No. 3 pin. When the large hydraulic jack returns to the zero position, pull out the No. 2 pin, move down one hole distance, and continue to start the three large hydraulic jacks to start the lifting work of the second stroke. When the second stroke lifting begins, pull out the No. 3 pin and use it after the jacking of the stroke is completed.
(6) When the chimney installation section has been lifted for several strokes and reaches the predetermined height, the assembled next cylinder unit is transported to the bottom of the lifting section by an electric vehicle, supported by six small hydraulic jacks, and after exiting the electric vehicle, the small hydraulic jacks are started to align with the upper chimney cylinder, weld and fix, and paint, and then the six small hydraulic jacks are slightly lifted so that the entire cylinder weight of the installation part is borne by the small hydraulic jacks.
(7) Remove the inner and outer ring beams, move them down to the bottom of the new installation unit, reinstall them, and lower the large hydraulic jacks and lifting rods at the same time, and then lift the second section in the order of (5) above. This cycle is repeated until the chimney cylinder is lifted to the designed position.
According to the design and specifications, chimney welding can be done by manual arc welding, semi-automatic or multi-functional full-position automatic welding.
During the entire chimney lifting process, measurement work is related to construction quality and lifting success. The measurement should be closely coordinated with the installation and strictly controlled to avoid error accumulation. The measuring instrument generally uses a laser theodolite. The verticality of the chimney is measured on two adjacent sides to control its deviation. The ambient temperature for measurement is relatively fixed, and the on-site temperature is generally around 20°C.
Yunbai Environment focuses on the research and development, production and sales of steel chimneys. We look forward to your call for consultation. Free service hotline: 4000-118-339, website: www.szhuading.com
